The present invention relates to air-inflated tires of automotive vehicles. More specifically, the invention relates to an electromagnetically activated pump for inflating the tires on such vehicles.
Tire pressure is one of the most important elements of drivability and safety on automotive vehicles. Insufficient tire pressure may cause excessive or uneven tread wear, decreased fuel efficiency, and poor traction. Although there are several common causes of improper tire pressure, most tires will lose air pressure on a day-to-day basis with normal use. Tires may lose up to and beyond one pound per square inch (psi) of air pressure per month.
It is proper practice, therefore, for an automotive vehicle operator to check and maintain tire pressure periodically to ensure adequate performance. Although it is recommended that a vehicle operator check tire pressure on a regular basis, adequate maintenance does not always occur. Furthermore, even when tire pressure is properly monitored, problems may surface. It is possible for a tire to acquire a slow leak, which an inexperienced or inattentive operator may not notice. Additionally, changes in ambient air temperature throughout the day can result in a significant change in tire pressure.
It is therefore desirable to provide a means for self-inflating a tire to counteract normal tire pressure loss. Some current self-inflating tire pumps rely on the centrifugal force created by tire rotation to initiate the action of the pump. However, such an approach to self-inflation is not available at all vehicle speeds, as such pumps are designed to be activated only when the centrifugal force exceeds a specific value. Furthermore, current self-inflation systems do not actually pump the needed air into the tire until the vehicle speed is reduced. The centrifugal force must return below the value needed for pump activation in order to initiate inflation.
Additionally, some pumps utilize tire pressure monitoring (TPM) systems. TPM systems communicate tire pressure status to the vehicle operator through intra-vehicular means such as a dashboard light or indicator. Vehicles equipped with a TPM system are often further equipped with a device such as an on-board compressor to correct air pressure deficiencies. When the TPM system detects a low tire pressure signal, it relays the information to the on-board compressor system, which then operates to inflate the corresponding tire. Such compressor systems are large and bulky and can be expensive to implement.
The present invention inrtegrates a tire pump with the wheel rim of a vehicle. The pump is activated electromagnetically to automatically inflate the tire when tire pressure is below a required value.
The pump extends from the atmosphere through the wheel rim and into the interior portion of the tire. The portion of the pump which is exposed to the atmosphere contains an air inlet for allowing air into the pump. A plunger within the pump operates to provide both opened and closed positions. In the open position, air from the atmosphere is allowed into the pump through the air inlet. When the plunger moves to the closed position, air is pushed through a valve into the inflatable portion of the tire.
The plunger is forced into the open position by a biasing element. The biasing element retains the plunger in the open position until an electromagnet is activated. The electromagnet, which is located on a vehicular component in close proximity with the wheel rim, reacts against the plunger, which is a permanent magnet, forcing the plunger into the closed position. The electromagnet, which is activated upon receiving a low tire signal from the vehicle""s body controller, reacts with the plunger when normal wheel rotation moves the pump within close proximity to the electromagnet. The biasing element returns the plunger to the open position when wheel rotation moves the pump out of the range of the electromagnet.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.